Question

A population is estimated to have a standard deviation of 8. We want to estimate the population mean within 2, with a 90% level of confidence.

How large a sample is required?

Answer 1

Solution :

Given that,

standard deviation =   =8

Margin of error = E = 2

At 90% confidence level

= 1 - 90%  

= 1 - 0.90 =0.10

/2 = 0.05

Z/2 = Z_{0.05 = 1.645}

sample size = n = [Z_/2* / E] ²

n = ( 1.645 * 8 / 2 )²

n =43